Automatically interlockable hinge fitting

ABSTRACT

A lockable hinge fitting which usually forms part of folding ladders, reclining chairs, etc., in which a pair of hinge arms are connected one to the other turnable round a common axis. One hinge arm carries a spring-loaded locking member which in its operative position locks the hinge fitting in a desired angular position by engaging one of a number of recesses circumferentially spaced apart from each other on the periphery of the other hinge arm. An unlocking lever is provided to move the locking member into its inactive position where the locking member is locked by a pawl. The pawl can be moved into its operative position in which it locks the locking member in its inactive position by pawl-actuating means during the movement of the unlocking lever in its unlocking position. This pawl actuating means is preferably an integral part of the unlocking lever or the pawl. According to the different attachments of the hinge fitting, the pawl will either release the locking member in any subsequent angular position defined by a recess or only when a suitable pivotable movement of the hinge fitting is performed. In both cases, the interlocking is performed automatically.

[ Feb. 22, 1972 AUTOMATICALLY INTERLOCKABLE HINGE FITTING [72] lnventor: Otto Mayer, Muhlstrasse 76, D-7067 Pluderhausen, Germany [22] Filed: Aug. 21, 1969 [21] Appl. No.: 851,974

[30] Foreign Application Priority Data Aug. 23, 1968 Germany ..P 17 75 524.7

[52] US. Cl ..16/144, 16/146 [51] Int. Cl ..E05d 11/10 [58] Field ofSearch ..l6/l44, 147

[56] References Cited UNITED STATES PATENTS 2,594,533 4/1952 Baker ..16/144 818,081 4/1906 Dwyer ..16/146 FOREIGN PATENTS OR APPLICATIONS 108,691 1/1968 Denmark..... ....16/146 402,312 11/1965 Switzerland ....16/l46 Primary ExaminerPaul R. Gilliam Attorney-Allison C. Collard [57] ABSTRACT A lockable hinge fitting which usually forms part of folding ladders, reclining chairs, etc., in which a pair of hinge arms are connected one to the other turnable round a common axis. One hinge arm carries a spring-loaded locking member which in its operative position locks the hinge fitting in a desired angular position by engaging one of a number of recesses circumferentially spaced apart from each other on the periphery of the other hinge arm. An unlocking lever is provided to move the locking member into its inactive position where the locking member is locked by a pawl. The pawl can be moved into its operative position in which it locks the locking member in its inactive position by pawl-actuating means during the movement of the unlocking lever in its unlocking position. This pawl actuating means is preferably an integral part of the unlocking lever or the pawl. According to the different attachments of the hinge fitting, the pawl will either release the locking member in any subsequent angular position defined by a recess or only when a suitable pivotable movement of the hinge fitting is performed. In both cases, the interlocking is performed automatically.

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OTTO MAYER WQ A Q ATTORNEY AUTOMATICALLY INTERLOCKABLE HINGE FITTING The present invention relates to lockable hinges.

More particularly, the present invention relates to an automatically lockable hinge where a pair of hinge arms are connected one to the other turnably round a common hinge axis, the first hinge arm carrying a movably mounted and springloaded locking member which is biased to engage in its operative position a recess provided in the second hinge arm and to define thereby preferred angular positions of both said hinge arms, an unlocking member being movably mounted with respect to said locking member and being movable between a first and a second position, a cam surface being provided on said unlocking member, and said locking member being biased to abut said cam surface which is so formed as to move said locking member into an inactive position, in which it is disengaged from said second hinge arm, when said unlocking member is being moved from its first position into its second position.

Hinges of this type usually form part of folding ladders, adjustable supports, reclining chairs, swiveling windows, folding cots, camping articles, etc.

It is a disadvantage of known hinges of this type that, after having moved the locking member into its inactive position, the unlocking member has to be actuated by the operator until the two hinge arms have been moved into the intended position. After having reached this position the unlocking member may be released, whereupon the locking member returns into its operative position and engages the second hinge arm, thus locking the hinge in its intended position.

Generally it is an object of the present invention to provide an improved hinge in which the unlocking member has not to be actuated during the rotating movement of the two hinge arms, thus enabling a more comfortable handling of articles equipped with a hinge or with hinges, and in which the locking member will return automatically into its operative position when the intended angular adjustment of the hinge has been reached.

It is another object of the present invention to provide a hinge in which the unlocking member is positioned adjacent one of the hinge arms when the hinge is in its locked state, so as to prevent from accidents caused by unintentional unlocking of the hinge, e.g., by an unintended step onto the unlocking member of a hinge of a folding ladder.

An additional object of the present invention is to provide a high degree of stability of the hinge in its locked position.

According to the invention there is provided a pawl being mounted movable with respect to said hinge axis and into and out of engagement with the unlocked locking member respectively, said pawl being frictionally connected with said second hinge am for common movement with respect to said hinge axis, said pawl being positioned in the path of a pawl-actuating member and being capable of being moved by said pawl-ac tuating member into locking engagement with said locking member when this locking member is situated in its inactive position, said pawl-actuating member being connected with said inlocking member at least during the movement of said unlocking member from its first into its second position to be move into cooperative engagement with said pawl.

It is a further object of the invention to provide a hinge which may be adapted to different fields of application in such a way that it is either pivotable only into the next defined angular position or into any desired angular position, after having unlocked the locking member; in the latter case the locking may be effected by a short counterrotation of the hinge after having passed the desired angular position.

Especially when installed in ladders or camping cots, there is one end position of the hinge in which both hinge arms are in a linear alignment, i.e., including an angle of 180. If the locking of both hinge arms can only be effected by a short counterrotation of the hinge arms by which they are pivoted in the direction from their widest opened position to their folded position, both hinge arms must have reached a position in which they include an angle of more than 180 to reach an angular position of 180 at the end of the necessary counterrotation. This makes it necessary to provide an appropriate and unsightly bead or recess within the outer surface of at least one of the hinge arms. Therefore, it is a further object of the present invention to provide means which release the locking member immediately before the hinge :reaches its completely opened end position, thus enabling a locking of the two hinge arms without any need for a counterrotation of the hinge arms from a position beyond this completely opened end position.

With respect to this object of the invention it is a preferred feature of the present invention that the pawl is provided with at least one face cam cooperating with said locking member during its movement into its inactive position, said face cam of the pawl being adapted to transmit a movement to said pawl during said movement of the locking member, by which movement of said pawl a stop face provided on said pawl is moved into the path of said locking member.

The invention, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments thereof when read in connecting with the accompanying drawings, in which:

FIG. 1 shows side elevations of a foldable ladder provided with hinges according to the present invention;

FIG. la shows the ladder in its folded position,

FIG. 1b shows the ladder as a scaffold bridge,

FIG. 10 shows another form of the ladder and FIG. 1d shows the ladder in a fourth form;

FIG. 2 is a sectional side view of a hinge according to the present invention in a first embodiment, locked in its completely opened end position;

FIG. 3 is a sectional side view of another embodiment of a hinge in an intermediate position between the folded and the completely opened position, the locking member being released but not yet in engagement with the second hinge arm, the control lever shown in FIG. 2 being omitted to show the other details more clearly;

FIG. 4 is a sectional side view of still another embodiment of a hinge according to the present invention and in a completely opened and unlocked position, the unlocking member being in its unlocking position;

FIG. 5a is a sectional side view of the embodiment shown in FIG. 4, however in an intermediate position and during a clockwise pivotal movement of the second hinge arm with respect to the first hinge arm, i.e., during a folding movement of the hinge;

FIG. 5b shows the locking member and two pawls of the hinge shown in FIG. 5a, however during a counterclockwise movement of the second hinge arm with respect to the first hinge arm;

FIG. 6 is a cross section taken along line VIVI of FIG. 5a;

FIG. 7 is a sectional side view of a further embodiment of a hinge according to the present invention in a completely opened and locked position;

FIG. 8 is a sectional side view of the embodiment shown in FIG. 7, however in its unlocked position;

FIG. 9 shows a sectional side view of the hinge shown in FIG. 8 during a clockwise pivotal movement of the second hinge arm with respect to the first hinge arm;

FIG. 10 is a sectional side view of a further embodiment of the present invention in a completely opened and locked position;

FIG. 11 is a sectional side view of a hinge similar to FIG. in a completely opened and unlocked position without the outer parts of the hinge;

FIG. Ila shows a pawl with face cams on both sides thereof and in a position similar to the position of the hinge shown in FIG. 11;

FIG. 12 is a sectional side view of the inner parts of a further embodiment of a hinge fitting according to the present invention in a completely opened position, the unlocking member being in its unlocking position;

FIG. I3 is a sectional side view of the embodiment shown in FIG. 12, the unlocking member being omitted and the hinge being in an intermediate position, in which the locking member is situated immediately before its engagement with a recess of the second hinge arm;

FIG. 14 shows the parts of the hinge shown in FIG. 13 in a position nearly halfway between the folded and the completely opened position:

FIG. 15 is a cross section of the hinge shown in FIG. 14 taken along the axis of the pivot bolt connecting both hinge arms;

FIG. 16 shows a section of a locking member formed without cutting; and

FIG. 17 shows a front elevation of the locking member seen in the direction as indicated in FIG. 16 by an arrow XVII.

As far as possible similar parts of the different embodiments are designated by like reference numerals.

The ladder shown in FIG. 1 comprises several straight beams 1, adjacent ends of which are interconnected by hinges 2. These hinges are arranged in such a way that they alternately have to be turned into their opened position in opposite directions. In their preferred positions shown in FIG. 1 the hinges can be locked. To unlock the hinges they are provided with unlocking members 3. Especially from FIG. 1b it may be seen that the unlocking members 3 of the central hinges are so positioned that in their locked position they lie adjacent and in parallel with one hinge arm. Thus it is impossible to unlock the hinge by mistake, e.g., by stepping onto this unlocking members, as this unlocking members must be turned away from the hinge arms if the hinge is to be unlocked.

The principle of the present invention will now be explained firstly by reference to a very simple embodiment of the invention, shown in FIG. 2.

In FIG. 2 the hinge 2 comprises a first hinge arm and a second hinge am 14, both pivotably connected for rotation round a common axis by a rivetted hinge bolt 12. Both hinge arms 10 and 14 are of substantially U-shaped cross section, thus forming sidewalls 10a, 10b, and 14a, 14b (See FIG. 6) respectively, in which the rivetted bolt 12 is mounted, and which enclose the inner parts of the hinge. The sidewalls 10a, 10b, and 14a, 14b are connected at one edge by bridge parts 10c and 14c, respectively. The other edges of the sidewalls 10a, 10b, and 14a, 14b, respectively, are flanged as it is indicated by reference characters 10d and 14d in FIG. 2, thus forming a substantially closed hollow section. The sidewalls 10a, 10b, 14a, 14b may be reinforced by reinforcing plates 16 concentrically arranged with respect to bolt 12, and mounted adjacent the outer or inner surface of these sidewalls.

The sidewalls 14a and 14b and the reinforcing plates 16 of the second hinge arm 14 are recessed at their periphery 18, the eircumferentially spaced recesses 20 defining a plurality of angular position in which the hinge may be locked. The opposite edges of each recess extend substantially in a radial direction with respect to the axis of bolt 12. The sidewalls 10a and 10b, and the adjacent reinforcement plates of the first hinge arm 10 are provided with parallel guides 22a and 22b (as shown in FIG. 6), which extend radially with respect to bolt 12. A locking member 24 is slidably guided by these guides 22a and 22b. A guide pin 26 is secured to the locking member 24 and extends through a bore 28 provided in an abutment 30 which is part of the first hinge arm 10. A compression spring 32 is clamped between the abutment 30 and the locking member 24.

A special recess 34 which serves to lock the hinge in its completely folded position is provided with an inclined edge 36 ascending towards the following recess 20. This inclined edge 36 will move the locking member against the action of spring 32 when the hinge is opened from its initially folded position, so as to enable locking member 24 to slide along the periphery 18 of the second hinge arm 14 and the respective reinforcement plate 16.

The sidewalls 14a and 14b of the second hinge arm 14 are positioned within the space between sidewalls 10a and 10b of the first hinge arm 10. Between sidewalls 14a and 14b a pawl 38 and a spacing sleeve 40 are pivotally mounted on bolt 12.

The unlocking member 3 is pivotally mounted on spacing sleeve 40. Adjacent locking member 24 the unlocking member 3 is provided with an eccentric cam surface 42 ascending radially with respect to bolt 12 towards an end stop 44. This cam surface is adapted to press locking member 24 against the action of spring 32 into its inactive position when the unlocking member 3 is pivoted in a counterclockwise sense. In its inactive position locking member 24 has left the respective recess 20 which it has been engaging. Between end stop 44 and a bearing bore 46, by which the unlocking member 3 is mounted on spacing sleeve 40, the unlocking member is provided with a catch 48 protruding in the path of pawl 38 and adapted to engage pawl 38 and to turn it in a counterclockwise sense when the unlocking member 3 is pivoted in the same sense.

The outer end of pawl 38 is bifurcated so as to form a recess 54 which is adapted to receive the locking member 24 when the locking member is engaging one of the recesses 20 or 34 if the pawl is situated in a suitable position. The contour of recess 54 is adapted to the contour of locking member 24. By a shoulder 56 the recess 54 is widened in the form of a step in its outer portion beyond periphery 18, the shoulder being provided in pawl arm 50 which limits recess 54 in clockwise direction. Thus, this pawl arm 50 has two substantially radially extending flanks 58 and 60, the inner flank 58 having a smaller distance from the opposed flank 62 of the other pawl arm 52 than the outer flank 60.

When unlocking the hinge by a counterclockwise turn of unlocking member 3, pawl 38 will be engaged by catch 48 at a moment at which locking member 24 has already been moved against the action of spring 32 as far as to enable shoulder 56 to slide into engagement with the front face 64 of locking member 24 until the outer flank 60 abuts the side face 66 of locking member 24.

The eccentrically ascending slope of cam surface 42 will not cause any self-locking between this cam surface and locking member 24. Assuming that during the unlocking of the hinge unlocking member 3 has been turned as far as possible in a counterclockwise sense, i.e., beyond that position in which pawl 38 is engaged by catch 48, and that unlocking member 3 will then be released, so locking member 24 will press against cam surface 42 and will thereby pivot the unlocking member 3 in a clockwise direction towards its initial or rest position until the front face 64 of locking member 24 will abut the shoulder 56 of pawl 38. Although the unlocking member 3 is now released, the locking member 24 can not return into its unlocked state and both hinge arms may be pivoted with respect to each other.

The pawl 38 is pivotably mounted on bolt 12 and is clamped between spacing sleeve 40 and sidewall 14a of the second hinge arm 14, so that pawl 38 abuts side wall 14a under axial pressure, thus providing a frictional connection between pawl 38 and the second hinge arm 14.

After having released the hinge in the position shown in FIG. 2, a pivotal movement can only be performed in a folding sense by turning the second hinge arm 14 in a clockwise direction with respect to the first hinge arm 10. During this movement pawl 38 is at first also pivoted in a clockwise sense by the frictional engagement of the second hinge arm 14 and pawl 38, until flank 62 of pawl arm 52 abuts the side face 68 of locking member 24. In this position the shoulder 56 has been moved out of engagement with the front face 64 of the locking member 24 so that this locking member 24 may now advance up to the periphery 18 of the second hinge arm 14, thereby further pivoting the unlocking member 3 towards its rest position by exerting pressure onto the cam surface 42. If the pivotal movement of the hinge is continued, a recess 20 will advance to an alignment with locking member member 24, so that the locking member can advance into this recess 20 and also into recess 54 of pawl 38, thereby further exerting pressure onto the cam surface 42 of unlocking member 3 and pivoting it back to its rest position.

pivotal movement can only be performed between two adjacent recesses 20 (or 34 respectively) as the locking member 24 will engage the next recess as soon as it comes into alignment with the locking member. If the hinge is in an intermediate position, when it is unlocked, and if the hinge is pivoted towards its opened position, i.e., a counterclockwise pivotal movement of the second hinge arm 14 with respect to the first hinge arm, pawl 38 abuts the side face 66 of locking member 24 permanently, due to the frictional engagement of pawl 38 and the second hinge arm 14. However, pawl 38 can not participate in the pivotal movement of the second hinge arm. Therefore shoulder 56 remains in its position engaging the front face 64 of the locking member so enabling the hinge to be pivoted across more than one defined hinge position, as the locking member can not engage one of the recesses 20. When the desired position has been reached it is necessary to continue the pivotal movement insignificantly and to then perform a short counterrotation in a counter clockwise sense by the second hinge arm with respect to the first hinge arm, thereby turning pawl 38 in the same sense and moving shoulder 56 out of engagement with the front face 64 of the locking member 24, so that the locking member may now advance to the periphery l8 and may snap into a recess 20, if the two hinge arms 10 and 14 are in suitable alignment (see FIG. 3).

As is obvious from the above, after having unlocked the hinge it may be pivoted towards its opened position as far as desired without any possibility for the locking member 24 to snap unintentionally into a recess 20. Also in its opened position, as shown in FIG. 2, in which the hinge arms are aligned in a 180 position, the locking member can not snap into its corresponding recess 20. Without further constructional details it is necessary to bring both hinge arms into an angular position of more than 180 and to perform a counterrotation from this position to release the locking member. The hinge as shown in FIG. 2 has an aesthetically designed and pleasing appearance without any unsightly recesses or beads in its outer surface. In the completely opened position of the hinge the bridge parts 10c and 140 form a continuous outer surface. Due to this latter constructional detail the hinge can not exceed its 180 position as is possible with the embodiments of hinges shown in FIGS. 3 to 9, because the bridge parts of these hinges are provided with recesses or beads.

The hinge shown in FIG. 2 is provided with a special device which immediately before both hinge arms reach their aligned, completely opened end position pivots pawl 38 out of its active position in which it locks locking member 24 in its inactive position, so as to enable the locking member 24 to snap into a recess as shown as the hinge reaches its completely opened position. This special device comprises a control lever 72 mounted on the first hinge arm 10 for pivotal movement round a pivot axis 70, which lies in parallel with the pivot axis of the hinge, and an extension 74 of the pawl arm 50 adapted to cooperate with the aforementioned control lever 72, and a cam 76 of the second hinge arm 14.

The control lever 72 is biased by a spring 78 in a clockwise sense. The control lever 72 is provided with two lugs 80 and 82, forming a recess 84 between these lugs, into which recess the extension 74 protrudes. Biased by the torsion spring 78 the control lever 72 abuts with its shorter lug 82 the outer edge of the extension 74. If the hinge is pivoted towards its opened position, immediately before reaching the 180 position the cam 76 abuts the lug 80 of the control lever 72 and turns this control lever 72 against the action of the torsion spring 78 in a counterclockwise sense during the further pivotal movement of the hinge, so that the shorter lug 82 engages the extension 74 and turns the pawl 38 in a clockwise sense as far as to reach the position shown in FIG. 2, and thereby enabling the locking member 24 to snap into the recess 20 when the hinge has reached its 180 position.

In FIG. 3 a further embodiment of the present invention is shown, which is similar to the hinge as viewed in FIG. 2 but is not provided with the special device for releasing the pawl 38 immediately before the completely opened position will be reached. This makes it necessary to provide the bridge part 1106 with a recess 10c and to provide the bridge part 14c with a bead Me, which, as may be seen from FIG. 4 more clearly, enables a pivotal movement exceeding the 180 position to be performed.

Referring now to FIGS. 4, 5, and 6, there is shown a hinge, which gives the possibility of pivoting the hinge, after having it unlocked, across a plurality of angular positions defined by recesses 20 either in a clockwise or in a counterclockwise sense, without any possibility for the locking member 24 to snap into one of the recesses 20, unless the locking is caused by a short counterrotation as has been explained above in connection with a counterclockwise pivotal movement of the second hinge arm 14.

The main difference between this embodiment and the embodiment shown in FIG. 2, is that the special device for releasing the pawl 38 has been omitted and that a second pawl 86 is pivotally mounted on bolt 12 between spacing sleeve 40 and the other sidewall 14b of the second hinge arm 14. This second pawl 86 is also clamped between its adjacent parts so that it abuts the sidewall 1417 under axial pressure, so as to provide a frictional engagement between this second pawl 86 and the second hinge arm 14. The outer end of the second pawl 86 is bifurcated so as to form a recess 88, which in suitable alignment with the locking member 24 enables locking member 24 to snap into its operative position. The second pawl 86 is provided with two pawl arms and 92, the pawl arm 92 corresponding with pawl arm 52 of the first pawl 38 being provided with a shoulder 94, so that a flank 96 of pawl arm 90 is opposed by an inner flank 98 of the second pawl arm 92 and by an outer flank 100. The distance between flanks 96 and 98 is smaller than the distance between flank 96 and the outer flank and corresponds with the distance between the side faces 66 and 68 of locking member 24. The distance between the outer flank 100 and the opposed flank 96 is much wider than the distance between flanks 60 and 62 of the first pawl 38. Furthermore, the flank 96 extends obliquely with respect to the radial direction, so that the recess 88 widens from its inner portion towards its outer portion. Thus, the locking member 24 can pivot the pawl 86 in a clockwise direction, when snapping into its operative position by engaging the oblique flank 96.

In FIGS. 5a and 5b pawl arm 52 of the first pawl 38 has been omitted to show more clearly the form of the second pawl 86. Furthermore in FIG. 5b the hinge arms 10 and 14 have been omitted.

When the unlocking member 3 is actuated the cam surface 42 urges the locking member 24 into its inactive position. Simultaneously the first pawl 38 is pivoted by the catch 48 as far as to move shoulder 56 under the front face 64 of the locking member 24 so as to lock member 24 in its inactive position. The second pawl 86 will substantially remain in its position in which recess 88 is in alignment with the locking member 24. If now the second hinge arm 14 is pivoted in a clockwise sense, as shown in FIG. 5a with respect to the first hinge arm 10, also both pawls 38 and :86 are pivoted in the same sense by the second hinge arm 14 which they are frictionally engaging. Shoulder 94 of the second pawl 86 has already been moved into the path of the locking member 24 until flank 100 abuts the side face 68 of the locking member 24 when the shoulder 56 leaves the range of the locking member 24. When shoulder 56 has completely left the range of locking member 24, the latter is only allowed to advance up to shoulder 94, the distance of which from the pivot axis, i.e., the axis of bolt 12, is less than the distance between shoulder 56 and that axis, but greater than the radius of the periphery 118. During further pivotal movement of the second hinge arm 14 in a clockwise sense, the second pawl 86 abuts locking member 24 and does not participate in this further pivotal movement. The first pawl 38 is further gpivoted by the second hinge arm 14 until its flank 62 abuts the side face 68 of locking member 24. To advance locking member 24 into one of the recesses 20 it is necessary to perform a counterrotation, i.e., a rotation in counterclockwise sense. As locking member 24 rests on shoulder 94, and as the distance between this shoulder 94 and the pivot axis is less than that between shoulder 56 and that pivot axis, the first pawl 38 can only be pivoted by the frictional engagement between the second hinge arm 14 and the first pawl 38 until flank 58 of the first pawl 38 abuts the side face 66 of locking member 24. The second pawl 86 is pivoted until shoulder 94 has left the range of locking member 24, so that locking member 24 can advance up to the periphery 18, from where it snaps into the next recess 20 when this comes into suitable alignment with the locking member. If the second pawl 86 has somewhat exceeded the suitable angula position, locking member 24 will come into engagement with the oblique flank 96 and will pivot the second pawl 86 in a clockwise direction, until recess 88 has completely received the locking member 24.

If the second hinge arm 14 is pivoted with respect to the first hinge arm 10 in a counterclockwise sense after having unlocked the hinge fitting (see FIG. b), the pawl 38 will remain in its position, which serves for locking the locking member 24, and the second pawl 86 will be pivoted in a counterclockwise sense until the outer end of pawl arm 90 abuts the side face 66 of the locking member 24. During further pivotal movement in a counterclockwise direction both the pawls 38 and 86 will abut locking member 24 and will not participate in the further pivotal movement, and locking member 24 remains in its inactive position. By a counterrotation in a clockwise direction shoulder 56 will leave the range of locking member 24 before the shoulder 94 of the second pawl 86 will reach the range of the locking member 24. In a similar manner as explained with respect to FIG. 2 the locking member 24 will advance to the periphery 18 of the second hinge arm 14 and will snap into the next recess when the pivotal movement is continued.

To positively obtain a frictional engagement between the pawls 38 and 86 and the second hinge arm 14, both pawls are slightly curved so as to elastically abut the adjacent sidewalls 14a and 14b, respectively. However, any other suitable means may be provided to obtain a frictional connection between the second hinge arm 14 and the pawls.

The bridgeparts c and 14c as viewed in FIG. 5a are somewhat different from that bridge parts shown in FIG. 4, as the bead 14e has a steplike form. Both these constructional details arc equivalent.

Referring now to FIGS. 7, 8, and 9 there is shown another hinge which, after having been unlocked, may be pivoted either in a clockwise or in a counterclockwise direction, and which can be locked by a short counterrotation. However, in this embodiment the unlocking member 3 is pivotably mounted on a bolt 110, which is secured to the first hinge arm 10. Two pawls 112 and 114 are pivotably mounted on bolt 12. Short extensions 112a and 1140 of the pawls 112 and 114 respectively exceed beyond bolt 12 on the side opposite to the main portions of the pawls. The unlocking member 3' is provided with a lever arm 116 having an upright catch 118 near its free end, which approaches the extensions 112a and 1144 during the unlocking movement of the unlocking member 3, thereby pivoting both the pawls 112 and 114 into their active position, as viewed in FIG. 8, in which these pawls are aligned with locking member 24. To obtain an accurate alignment the lever arm 116 is provided with a second upright catch 120 and both these catches 118 and 120 are so positioned that they will engage the edges 112k and 114b of the pawls 112 and 114 respectively on different sides of the bolt 12. Thus, a rotational movement of pawls 112 and 114 is prohibited when these pawls abut the catches 118 and 120.

The end of the first pawl 112 adjacent the locking member 24 is tapered so that its front face 122 is as broad as the front face 64 of the locking member 24. The front face 122 of the pawl 112 is a stop which serves for locking the locking member 24 in its inactive position. The end of the second pawl 114 is bifurcated so as to form a recess 128 the contour of which corresponds with the contour of locking member 24. In a greater distance from the hinge axis than the radius of the periphery 18 the pawl arms 124 and 126 are provided with shoulders 130 and 132 respectively, which are adapted to cooperate with the front face 64 of locking member 24. The distance between the shoulders 130 and 132 and bolt 12 is somewhat less than the distance between the front face 122 of the first pawl 112 and bolt 12. To limit the pivotal movement of the first pawl 112 in a clockwise direction the outer edge of pawl arm 124 is provided with a stop 136, which protrudes in the path of the first pawl 112. The pivotal movement of the second pawl 114 is limited by the pawl arms 124 and 126 which will abut the locking member 24.

Contrary to the embodiments described above the cam surface 42 of unlocking member 3 is short and is provided on a lever arm 138 which abuts the spacing sleeve 40 in the rest position of the unlocking member 3', i.e., when the hinge is locked.

The locked position is viewed in FIG. 7. By pivoting the unlocking member 3 in a counterclockwise sense the cam surface 42' moves the locking member 24 against the action of the spring 32 out of its operative position, in which it engages one of the recesses 20. Simultaneously the catches 118 and 120 pivot pawl 112 in a counterclockwise sense so that its stop or front face 122 engages the front face 64 of the locking member 24, thereby holding the locking member 24 in its inactive position when the unlocking member 3 has been released. When the second hinge arm 14 is pivoted with respect to the first hinge arm in a clockwise direction, as viewed in FIG. 9, the frictional engagement of pawls 112 and 114 with the second hinge arm 14 will pivot pawl 112 out of the range of locking member 24 and will simultaneously move shoulder 132 under the front face 64 of the locking member 24, thereby still holding locking member 24 in its inactive position, but in a position a little bit nearer to bolt 12 than before. Simultaneously the unlocking member 3 has been moved back into its initial position. During a further pivotal movement of the second hinge arm 14 in a clockwise direction pawl arm 126 abuts the side face of locking member 24 and the first pawl 112 abuts stop 136 so that both pawls can not participate in any further pivotal movement since locking member 24 still rests on the shoulder 132. By a short counterrotation of the second hinge arm 14, i.e., in counterclockwise sense, the second pawl 114 will be pivoted until locking member 24 leaves the shoulder 132 and is free to advance up to the periphery 18. The first pawl 112 abuts the side face 66 of locking member 24 and can not prevent the advancing movement of the latter. As soon as one of the recesses 20 comes into alignment with locking member 24 the locking member will snap into its operative position.

If the second hinge arm 14 is pivoted in a counterclockwise direction after having been unlocked, pawl 112 will move out of the range of locking member 24 in the same direction, while the shoulder 130 will move under the front face 64 of the locking member 24. Thereby the unlocking member 3 has been moved back into its initial position. The locking member 24 rests on the shoulder 130 until a counterrotation of the second hinge arm 12, i.e., in clockwise direction, enables locking member 24 to leave shoulder 130 and to advance up to the periphery l8 and to snap into one of the recesses 20.

The special device as shown in FIG. 2 which is adapted to release locking member 24 shortly before the completely opened end position of the hinge will be reached, needs an additional torsion spring 78 and an additional pin 70. It is therefore a somewhat expensive detail which may be avoided by the embodiment of a hinge according to FIGS. 10 to 17.

Referring now to FIGS. 10 and 11 the spacing sleeve 40 is surrounded by a shorter spacing sleeve 40a on which is pivotably mounted the unlocking member 3. A pawl 38a is mounted on the sleeve 40 which has a bifurcated end similar to the above described embodiments. The bifurcated end is provided with a recess 54a to receive the locking member 24.

The pawl arms 140 and 142 of the pawl 38a have a different form. At one side of the locking member 24 the pawl 3311a has a pawl arm 140 which is hooklike and bent towards locking member 24. The inner flank 144 of this pawl arm 1411 forms a surface cam which is adapted to cooperate with locking member 24 when the latter is moved into its inactive position by means of the unlocking member 3. The other flank 144 is provided with a shoulder 148 which divides the flank 146 to form an inner portion 146a and an outer portion 1413b. It can easily be seen from FIG. 10 that by the form of surface cam 144 the locking member 24 will pivot the pawl 311a in clockwise sense when the locking member 24 is moved into its inactive position, thereby moving the shoulder 14% into alignment with the front face 64 of locking member 24. After having released the unlocking member 3, under the influence of the spring 32 which urges the locking member 24 against the cam surface 42, the unlocking member 3 will return into its in itial position until locking member 24 will abut shoulder 48 as viewed in FIG. 11.

Assuming that the unlocking has been performed in an intermediate position of the hinge, the second hinge arm 14 may now be pivoted either on a clockwise or in a counterclockwise direction with respect to the first hinge arm 10.

If the second hinge arm 14 is pivoted in a counterclockwise direction, due to the frictional connection between pawl 311a and the sidewall 14a of the second hinge arm 14, pawl 38a is also pivoted in a counterclockwise direction with respect to the first hinge arm 10 and locking member 24 until the surface cam 144 abuts the locking member 24, whereby the shoulder 148 leaves the range of the locking member 24 and releases it, which may now advance towards bolt 12 until the locking member 24 abuts the periphery 18 of the sidewalls 14a and 14b and the reinforcement plate 16. By this advancing move ment of locking member 24 towards the periphery 18 the locking member 24, which is still abutting the cam surface 42 of the unlocking member 3, has further pivoted the latter towards its initial position. If the pivotal movement of the second hinge arm 14 in a counterclockwise direction is continued the next recess 20 will be aligned with locking member 24 so as to enable the latter to snap into this recess to lock the hinge in this angular position.

If the second hinge arm 14 is pivoted in a clockwise sense after having moved the locking member 24 into its inactive position, the sidewall 14a will also try to move pawl 38 in the same direction. However, the flank portion 14Gb of pawl 38a is abutting the side face 68 of locking member 24 and can not perform any pivotal movement in a clockwise direction. Therefore, during the continuation of the pivotal movement of the second hinge arm 14 in a clockwise direction the locking member 24 remains in its inactive position. This state may be changed by counterrotating the second hinge arm 14 in a counterclockwise direction which, due to the aforementioned frictional engagement will also move the pawl 34a in a counterclockwise sense, thereby causing the shoulder 148 to release locking member 24 which now wili advance up to the periphery 18, and will snap into the next recess 20 when this recess comes into suitable alignment with the locking member 24.

The embodiment described with reference to FIGS. 10 and 11 makes it possible to pass several recesses 20 during a pivotal movement of the hinge from its opened position towards its folded position without any locking of the hinge. If the hinge is to be locked in a desired position, a short counterrotation is necessary to release the locking member 24. However, in the opposite direction i.e., from the folded position towards the opened position, the hinge will be automatically locked in each angular position defined by a recess 20. As is obvious, this locking takes place at that very moment at which the hinge reaches an angular position defined by a recess 21 without any need for a counterrotation. Therefore the hinge will also be locked in its completely opened end position without any need for exceeding beyond this end position, so that this embodiment is an advantage with respect to the additional or special device shown in FIG. 2.

If a hinge is needed which automatically locks the hinge as soon as the next defined angular position is reached, pawl 38a has to be replaced by a pawl 311b, as viewed in FIG. 11a. Pawl 38b is provided with two surface cams 144 and 144" at both sides of the locking member 24. Between both surface cams 144' and 144" there is positioned a radially and outwardly extending projection 150, the outer end of this projection form ing a stop face 144 cooperating with this front face 64 of the locking member 24. At both sides of the projection there are provided recesses 154a and l54b respectively, which are adapted to receive the locking member 24 in its operative position. As is obvious from FIG. 11a, locking member 24 will either contact the surface cam 144' or the surface cam 144" during its movement into its inactive position, thereby pivot ing pawl 34b in such a direction that the projection 150 is moved under the front face 64 of locking member 24, thereby locking the locking member in its inactive position. If the second hinge arm 14 is now pivoted with respect to the first hinge arm 11) in one of the possible directions, pawl 38b is moved so that the projection 150 releases the locking member 24, due to the frictional connection between pawl 38b and the second hinge arm 14, thereby enabling the locking member 24 to advance into one of the recesses 154a or 154b respectively as soon as a recess 20 is in suitable alignment with the locking member 24.

As has already been mentioned it may be desirable to have a hinge which gives the possibility of turning the hinge in both directions across a plurality of recesses 20 without any possibility for the locking member 24 to lock the hinge unintentionally, but only after a short counterrotation of the hinge. Such a hinge can be obtained by adding a second pawl 86a to a hinge as shown in FIGS. 10 and 11. The second pawl 86a is pivotally mounted on the spacing sleeve 40, however on the other side of the unlocking lever 3, as can be seen from FIG. 15. The second pawl 86a is frictionally connected with sidewall 14b of the second hinge arm 14 so as to be pivotable together with the second hinge arm. This embodiment is now explained with reference to FIGS. 12 to 15.

It is to be noted, that a trouble-free function of the hinge does not demand a positioning of the pawls on different sides of the unlocking member 3, as has been shown only by way of example. Any other arrangement is possible, provided that a frictional engagement of the pawls and the second hinge arm is possible. So it is possible to secure a friction plate to the second hinge arm 14 for common rotation therewith and to provide a frictional connection between one pawl or both pawls and this friction plate while the unlocking member may be situated adjacent one of the sidewalls 14a or 14b.

The end of the second pawl 86a is bifurcated so as to provide a recess 88a which is adapted to receive the locking member 24 in its operative position, as viewed in FIG. 13. The recess 48a is wider than the distance between the side faces 66 and 63 of locking member 24. Lateral flanks of recess 8811 are provided near its outer end with steplike shoulders 148a and 14812. The distances of these shoulders of the second pawl 86a from the pivot axis of the hinge, i.e., the axis of bolt 12, is such that the shoulder 148a, being situated on the same side of the recess 88a as shoulder 148 of the first pawl 34a, has a smaller distance from the periphery 18 of the second hinge arm 14 than shoulder 14%, and that shoulder 148b on the side of the surface cam 144 of the first pawl 38 is situated somewhat nearer to the periphery 18 than shoulder 144a. However, the shoulders 148, 148a, and 148k lie outwards from the periphery 1d of the second hinge arm 14, so as to enable shoulder 148b to prevent locking the member 24 from engaging one of the recesses 20 of the secondl hinge arm 14.

In this embodiment the inclined edge 36 of the special recess 34 ends in a cam 35, which protrudes over the circular part of the periphery 18 of hinge arm 14 in such an extent that the top of the cam 35 has a somewhat greater distance from the pivot axis than the second shoulder 148b of the second pawl 46a.

To show this embodiment very clearly unlocking member 3 is only shown in FIGS. 12 and 15, and not in FIGS. 13 and 14.

The position of the elements of the hinge shown in FIG. 12 corresponds to an unlocked position in which the unlocking member 3 has been pivoted in a counterclockwise sense to move locking member 24 into its inactive position. By engagement between locking member 24 and cam surface 144 the first pawl 38a has been moved in a clockwise direction and the shoulder 148 has been moved under the front face of locking member 24 to lock the locking member in its inactive position.

As in its operative position locking member 24 was within recess 88a or the second pawl 86a and as this second pawl is not moved during the unlocking movement of unlocking member 3, locking member 24, and the first pawl 380, the second pawl 86a will remain in its position shown in FIG. 12, the hinge remains in its unlocked position and may, if this is an intermediate position, be pivoted in either direction.

If the second hinge arm 14 is pivoted with respect to the first hinge arm in a counterclockwise direction both pawls 38a and 86a will be pivoted in the same direction, and thereby at first the second shoulder 14% of the second pawl 86a will move under locking member 24, and then the shoulder 148 of the first pawl 38a will release the locking member to advance towards shoulder 148b, and finally pawl arm 140 of the first pawl 38a and the corresponding pawl arm 90a of the second pawl 86a will abut the side face 66 of locking member 24, thereby preventing both pawls 38a and 860 from any further movement. In this position the pivotal movement of the second hinge arm 14 may be continued without any locking movement of locking movement 24. The locking of the hinge can only be effected when the second hinge arm 14 performs a short counterrotation in a clockwise direction, as such a pivotal movement will pivot both pawls 38a and 86a only so far that the flanks of the recesses 54a and 88 adjacent shoulders 148 and 148a respectively abut the side face of locking member 24 due to the fact that locking member 24 has already been advanced up to the shoulder l48b which lied closer to the periphery 18 than shoulders 148 and 148a. However, the pivotal movement of both pawls is sufficient to release the locking member 24 from the shoulder 1481: so that locking member 24 may advance up to the periphery 18 from where it will snap into the next recess 20 coming into suitable alignment. In FIG. 14 is shown the position of the elements of the hinge during a pivotal movement of the second hinge arm 14 in a counterclockwise direction and before the counterrotation has begun.

If the hinge is unlocked and the second hinge arm 14 is pivoted in a clockwise direction with report to the first hinge arm 10 the second pawl 86a is also pivoted in a clockwise direction until the outer flank portion of recess 88a abuts the side face 68 of the locking member 24, thereby bringing the shoulder 148a into the path of the locking member 24. As already has been mentioned the locking member 24 rests on the shoulder 148 since the unlocking movement has been finished. If the pivotal movement of the second hinge arm 14 in a clockwise direction is continued the elements remain in their respective positions and there is no possibility for the locking member 24 to snap into one of the recesses 20. When a short counterrotation in counterclockwise direction is performed, the pawls 38a and 86a are pivoted in the same direction, so that the shoulder 148 releases the locking number 24 before the second shoulder l48b of the second pawl 86a comes into the path of locking member 24. This enables locking member 24 to advance up to the periphery 18 of the second hinge arm 14, from where it will snap into the next recess 20 which comes into suitable alignment. To insure that the shoulder 148!) will not hinder the advancing movement of locking member 24 towards the periphery 18, recess 88a of the second pawl 86a is preferably wider than the corresponding contour of the locking member 24.

If the hinge is in its completely folded position, locking member 24 engages the special recess 34. If the hinge is opened from this folded position, locking member 24 slides along the inclined edge 36 until it reaches the top of cam 35. Thereby the locking member 24 has been lifted to such an extent that the second shoulder 148!) of the second pawl 860 can be moved under the front face 64 of the locking member 24, thereby holding the locking member 24 in its inactive position, so that a continuation of the pivotal movement of the hinge can not be interrupted by the locking member 24 until a short counterrotation is performed, which will enable the locking member 24 to engage one of the recesses 20.

In order to make the frictional connection between the pawls and the sidewalls 14a and 14b respectively of the second hinge arm 14 as much as possible independent from the tensile stress within bolt 12, the pawls 38a and 86a are mounted on a spacing sleeve extending between the reinforcement plates. Since the unlocking member 3 is mounted on a shorter sleeve 40a surrounding the spacing sleeve 40, the unlocking member is mounted between both pawls 86a and 38a.

In some applications of the improved hinge according to the present invention, e.g., adjustable head rests in automobiles, adjustable telephone swivel arms, or more generally, hinges with an axially branching arm which is pivotable around 360, etc., it is of advantage if the unlocking member 3 is not mounted on bolt 12 but on the first hinge arm 10, as bolt 12 is not within the normal range of the hand of the operating person. The unlocking member 3 may be formed as a one or a double armed hand lever which is connected with the locking member 24 or an extension thereof, e.g., the guide pin 26, by a linkage, cable, Bowden cable, etc.

Especially the embodiments shown in FIGS. 10 to 15 make it possible to produce hinges by a simple mass production without expensive cutting operations. Therefore it is an advantage if the locking member 24 is also manufactured without a cutting operation. The locking member as shown in FIGS. 16 and 17 is made from coiled stock by punching and is the bent in form of an oblong ring. An upset pin 26 can simultaneously with this bending step be secured to the locking member by pressing. By this method favorable radii may be obtained at 24b, 24c, and 24d, which hitherto have been machined by cutting operations. These radii are important with respect to the engagement between the locking member, the guide for the locking member in hinge arm 10, and the several recesses which are adapted to receive the locking member.

The proposed form of the locking member 24 enables the production of a universally applicable, unexpensive, and reliable hinge.

It is to be noted that hinges according to the present invention are especially advantageous in constructions where a number of hinges have to be pivoted simultaneously, since after having actuated the unlocking members of the hinges the hinges can be adjusted at least in the next hinge position without any need for a continued actuating of the unlocking members.

The embodiments shown in FIGS. 4 to 6, 7 to 9, and 12 to 15 can be provided with a torsion spring which biases the hinge arms 10 and 14 into their folded position. This is advantageous especially in reclining seats for automobiles and it makes it possible to adjust the hinge on both sides of the seat by reclining or by performing a movement of the body in opposite direction when an unlocking member on one side of the seat has been actuated which is also connected to the unlocking member of the hinge at the other side of the reclining seat. Thus, it is possible to actuate the unlocking member for a very short period by one hand and then to adjust the reclining seat without any necessity of taking off the hands from the steering wheel.

If coaxially aligned hinges are used in pairs the bolts (see FIGS. 7 to 9) can be made in the form of a connecting rod which may be connected rigidly between the unlocking members 3 and which may serve as a step when the hinges are attached to ladders. In this case preferably only one unlocking member is provided with a handle. Furthermore, this connecting rod may be enclosed by a protective tube.

Bolt 12 may be divided in a radial plane and may be formed as a tubular rivet on opposite sides of the hinges. The connecting rod which is rigidly connected between the unlocking members of both hinges may be mounted within the bores of the tubular rivets. However, it is also possible to form the tubular rivets of the coaxially aligned hinges as one single connecting tube so that a rod connecting the unlocking members of both hinges may be mounted within this connecting tube.

lclaim:

1. An automatically lockable hinge fitting, comprising;

a first hinge arm pivotably mounted about a hinge axis;

a second hinge arm, pivotably mounted about said hinge axis, having a circular portion concentric with respect to said hinge axis and at least one recess provided in the peripheral portion thereof;

a movably mounted, spring-loaded locking member carried by said first hinge arm and slidably guided therein sub stantially radially with respect to said hinge axis, said locking member being biased to engage in an operative position said recess provided in said second hinge arm and thereby define preferred angular positions of both of said hinge arms;

an unlocking member, pivotably and coaxially mounted with respect to said hinge axis and pivotable between a first and second position, said unlocking member having a cam surface provided thereon which abuts said locking member and moves said locking member to an inoperative position in which it is disengaged from said second hinge arm as said unlocking member is pivoted from its first to its second position;

a pawl, pivotably and coaxially mounted with respect to said hinge axis, and movable into and out of engagement with said locking member when said locking member is situated in its inoperative position, said pawl being frictionally coupled to said second hinge arm so as to provide common movement therewith with respect to said hinge axis, and being bifurcated at its outer end so as to provide pawl arms at both sides of said locking member and a recess at the outer end of said pawl, the contour of said recess substantially conforming in its inner portion to the contour of said locking member and widening in its outer portion to form a shoulder in the pawl arm situated on the side of said locking member which is approached when said unlocking member is pivoted from its first to its second position, the radial distance between said shoulder and said hinge axis being longer than the radius of the periphery of said circular portion of said second hinge arm; and

a pawl abutment member, affixed to said unlocking member and disposed in the pivotable path of said pawl, for engaging and moving said pawl into locking engagement with said locking member whenever said locking member is situated in its inoperative position, said abutment member engaging said pawl during movement of said unlocking member from its first to its second position,

a catch pivotably mounted on said first hinge arm engaging one arm of said pawl, and a cam surface provided on said second hinge arm, for engaging said catch and pivoting said pawl when said first and second hinge arms approach 180 alignment, and thereby aligning said recess provided in said pawl with said locking member and allowing said locking member to be received by said recess so as to lock said first and second hinge arms with respect to each other,

a second pawl, pivotably and coaxially mounted with respect to said hinge axis and frictionally coupled to said second hinge arm, the outer end of said second pawl being bifurcated so as to provide pawl arms at both sides of said locking member and a recess at said outer end, the contour of said recess substantially conforming in its inner portion to the contour of said locking member and widening in its outer portion to form a shoulder in the pawl arm situated at the side of said locking member which is approached by said second pawl when said second hinge arm is pivoted, the radial distance between said shoulder of said second pawl and said hinge axis being shorter than the radial distance between said shoulder of said first pawl and said hinge axis, but longer than the radius of the periphery of said circular portion of said second hinge arrn, said recess in said second pawl being wider than said recess in said first pawl in the range of said shoulders, said pawl arm of said second pawl which is opposite said pawl arm provided with said shoulder being provided with a flank extending from the inner end of said recess substantially obliquely with respect to the radial direction about said hinge axis, in order to widen said recess at its outer portion so that during the movement of said locking member from its inoperative position to its operative position, said locking member contacts said flank and pivots said second pawl into a position suitably aligned with respect to said locking member, in which aligned position said pawl arm provided with said flank is moved out of the range of said shoulder which is provided in said pawl arm of said first pawl.

2. An automatically lockable hinge fitting, comprising;

a first hinge arm pivotably mounted about a hinge axis,

a second hinge arm, pivotably mounted about said hinge axis, having at least one recess provided in a circular, peripheral portion thereof,

a movably mounted, spring-loaded locking member, carried by said first hinge arm, biased to engage in an operative position said recess provided in said second hinge arm and define thereby preferred angular positions of both of said hinge arms, an unlocking member, movably mounted about said hinge axis, and pivotable between a first and second position, said unlocking member including a cam surface which abuts said locking member and moves said locking member into an inoperative position in which it is disengaged from said second hinge arm as said unlocking member is pivoted from its first position to its second position, and

a pawl, pivotably mounted on an axle parallel with said hinge axis, and movable into and out of engagement with said locking member when said locking member is situated in its inoperative position, said pawl being frictionally connected with said second hinge arm for common movement therewith with respect to said hinge axis, and bifurcated so as to provide pawl arms at both sides of said locking member and a recess at the outer end of said pawl which cooperates with said locking member, the contour of said recess substantially conforming in its inner portion to the contour of said locking member and widening at its outer portion to form a shoulder on one of said pawl arms on said pawl, the radial distance between said shoulder and said hinge axis being longer than the radius of the periphery of said circular portion of said hinge arm, and a face cam on the other pawl arm of said pawl, said cam cooperating with said locking member during movement into its inoperative position and transmitting movement to said pawl during movement of said locking member, so that a stop face provided on said pawl is moved into the path of said locking member,

a second, pivotably mounted pawl, the outer end of which is bifurcated so as to provide pawl arms at both sides of said locking member and a recess at the outer end of said second pawl which cooperates with said locking member, the contour of said recess substantially conforming in its inner portion to the contour of said locking member and widening in its outer portion to form a shoulder at each pawl arm of said second pawl, said recess being wider than the recess in said first pawl, said shoulder of said second pawl being disposed on the side of said pawl being disposed on the side of said pawl corresponding to said shoulder provided on said first pawl, and said shoulder of said second pawl being disposed on the side of said first pawl provided with said surface cam and having a shorter which said inclined edge ends, the top of which has a longer distance from said hinge axis on said first shoulder of said second pawl, said first shoulder and said inclined edge of said recess being situated at the same side of said second pawl and said recess, respectively.

l l k k 

1. An automatically lockable hinge fitting, comprising; a first hinge arm pivotably mounted about a hinge axis; a second hinge arm, pivotably mounted about said hinge axis, having a circular portion concentric with respect to said hinge axis and at least one recess provided in the peripheral portion thereof; a movably mounted, spring-loaded locking member carried by said first hinge arm and slidably guided therein substantially radially with respect to said hinge axis, said locking member being biased to engage in an operative position said recess provided in said second hinge arm and thereby define preferred angular positions of both of said hinge arms; an unlocking member, pivotably and coaxially mounted with respect to said hinge axis and pivotable between a first and second position, said unlocking member having a cam surface provided thereon which abuts said locking member and moves said locking member to an inoperative position in which it is disengaged from said second hinge arm as said unlocking member is pivoted from its first to its second position; a pawl, pivotably and coaxially mounted with respect to said hinge axis, and movable into and out of engagement with said locking member when said locking member is situated in its inoperative position, said pawl being frictionally coupled to said second hinge arm so as to provide common movement therewith with respect to said hinge axis, and being bifurcated at its outer end so as to provide pawl arms at both sides of said locking member and a recess at the outer end of said pawl, the contour of said recess substantially conforming in its inner portion to the contour of said locking member and widening in its outer portion to form a shoulder in the pawl arm situated on the side of said locking member which is approached when said unlocking member is pivoted from its first to its second position, the radial distance between said shoulder and said hinge axis being longer than the radius of the periphery of said circular portion of said second hinge arm; and a pawl abutment member, affixed to said unlocking member and disposed in the pivotable path of said pawl, for engaging and moving said pawl into locking engagement with said locking member wheNever said locking member is situated in its inoperative position, said abutment member engaging said pawl during movement of said unlocking member from its first to its second position, a catch pivotably mounted on said first hinge arm engaging one arm of said pawl, and a cam surface provided on said second hinge arm, for engaging said catch and pivoting said pawl when said first and second hinge arms approach 180* alignment, and thereby aligning said recess provided in said pawl with said locking member and allowing said locking member to be received by said recess so as to lock said first and second hinge arms with respect to each other, a second pawl, pivotably and coaxially mounted with respect to said hinge axis and frictionally coupled to said second hinge arm, the outer end of said second pawl being bifurcated so as to provide pawl arms at both sides of said locking member and a recess at said outer end, the contour of said recess substantially conforming in its inner portion to the contour of said locking member and widening in its outer portion to form a shoulder in the pawl arm situated at the side of said locking member which is approached by said second pawl when said second hinge arm is pivoted, the radial distance between said shoulder of said second pawl and said hinge axis being shorter than the radial distance between said shoulder of said first pawl and said hinge axis, but longer than the radius of the periphery of said circular portion of said second hinge arm, said recess in said second pawl being wider than said recess in said first pawl in the range of said shoulders, said pawl arm of said second pawl which is opposite said pawl arm provided with said shoulder being provided with a flank extending from the inner end of said recess substantially obliquely with respect to the radial direction about said hinge axis, in order to widen said recess at its outer portion so that during the movement of said locking member from its inoperative position to its operative position, said locking member contacts said flank and pivots said second pawl into a position suitably aligned with respect to said locking member, in which aligned position said pawl arm provided with said flank is moved out of the range of said shoulder which is provided in said pawl arm of said first pawl.
 2. An automatically lockable hinge fitting, comprising; a first hinge arm pivotably mounted about a hinge axis, a second hinge arm, pivotably mounted about said hinge axis, having at least one recess provided in a circular, peripheral portion thereof, a movably mounted, spring-loaded locking member, carried by said first hinge arm, biased to engage in an operative position said recess provided in said second hinge arm and define thereby preferred angular positions of both of said hinge arms, an unlocking member, movably mounted about said hinge axis, and pivotable between a first and second position, said unlocking member including a cam surface which abuts said locking member and moves said locking member into an inoperative position in which it is disengaged from said second hinge arm as said unlocking member is pivoted from its first position to its second position, and a pawl, pivotably mounted on an axle parallel with said hinge axis, and movable into and out of engagement with said locking member when said locking member is situated in its inoperative position, said pawl being frictionally connected with said second hinge arm for common movement therewith with respect to said hinge axis, and bifurcated so as to provide pawl arms at both sides of said locking member and a recess at the outer end of said pawl which cooperates with said locking member, the contour of said recess substantially conforming in its inner portion to the contour of said locking member and widening at its outer portion to form a shoulder on one of said pawl arms on said pawl, the radial distance between said shoulder and said hinge axis being longer than the radius of the periphery of said circular portion of said hinge arm, and a face cam on the other pawl arm of said pawl, said cam cooperating with said locking member during movement into its inoperative position and transmitting movement to said pawl during movement of said locking member, so that a stop face provided on said pawl is moved into the path of said locking member, a second, pivotably mounted pawl, the outer end of which is bifurcated so as to provide pawl arms at both sides of said locking member and a recess at the outer end of said second pawl which cooperates with said locking member, the contour of said recess substantially conforming in its inner portion to the contour of said locking member and widening in its outer portion to form a shoulder at each pawl arm of said second pawl, said recess being wider than the recess in said first pawl, said shoulder of said second pawl being disposed on the side of said pawl being disposed on the side of said pawl corresponding to said shoulder provided on said first pawl, and said shoulder of said second pawl being disposed on the side of said first pawl provided with said surface cam and having a shorter distance from said hinge axis than the other shoulder of second pawl, said circular portion of said second hinge arm includes a plurality of recesses on its periphery, the last one of said recesses having a lateral edge which is inclined and ascends towards the periphery of said circular portion, a cam being provided on said periphery at the point at which said inclined edge ends, the top of which has a longer distance from said hinge axis on said first shoulder of said second pawl, said first shoulder and said inclined edge of said recess being situated at the same side of said second pawl and said recess, respectively. 